This invention relates to low water cutoff conductance probe controls, and more particularly to a conductance probe and control with both temperature setpoint and differential adjustment. As known in the prior art, the operation of a steam boiler is controlled by pressure and a low water cutoff control. One type of low water cutoff control is known from U.S. Pat. No. 4,263,587 (John). Sometimes, a high limit temperature safety control is also utilized. Hot water boilers are controlled by an aquastat temperature control, and on higher BTU capacity boilers, a low water cutoff is required. Typically, these are separate controls, each control requiring a separate mounting hole or fitting in the boiler shell.